Stretch fabric and method of making same



United States Patent No Drawing. Filed June 9, 1965, Ser. No. 462,750 11 Claims. (Cl. ZS- IS) The present invention relates to the preparation of stretch fabric from cotton or other cellulosic textile material. More particularly, the invention is concerned with a process for preparing cellulosic stretch fabric which possesses a high degree of recoverable stretch along with other desirable characteristics, such as enhanced wash and wear properties.

Numerous efforts have previously been made to prepare stretch fabrics. In one such process (see US. Patent 3,145,132), fabric is slack mercerized using caustic soda followed by the application of thermoplastic or thermosetting resins or reactive agents. It is well known that this type of slack mercerization will give some stretch because of the fabric shrinkage which occurs. However, the maximum potential stretch, based on the amount of fabric shrinkage which occurs, is not realized.

Other techniques for preparing stretch fabric involve the use of stretch or crimped yarns, e.g. yarns which have been false twisted, core spun or given a high torque. However, these methods, While useable, suffer from one disadvantage or another. For example, there are problems in handling stretch or lively yarns and yarn tension in Weaving must be carefully controlled to obtain con sistent results. Resin treatments of yarns have also been proposed to facilitate the preparation of stretch yarns see, for example, U.S. Patent 3,025,659 which describes the resin pretreatment of cotton yarns to render same functionally thermoplastic for false twisting). However, such resin application tends to make the treated yarns weaker with resultant loss in weaving efficiency.

As will be appreciated from the foregoing, there is considerable room for improvement in the preparation of stretch fabrics from cotton and like cellulosic yarns. Accordingly, the principal object of the present invention is to provide certain improvements in cellulosic stretch fabric and procedures for making the same whereby prior disadvantages of the type indicated are obviated. A more specific object of the invention is the provision of a stretch fabric comprising cotton or the like which is characterized by its high degree of recoverable stretch and enhanced wash and wear properties among other desirable characteristics. Further objects will also be apparent from the following description of the invention.

Broadly stated, the objects of the invention are accomplished by (1) providing a plied yarn made by plying together two or more ends of cotton or other type of cellulosic yarn having an initial twist therein which is in the same direction as the ply twist (i.e. twist-ontwist); (2) making a fabric with this plied yarn; (3) washing the resulting fabric to cause the fabric to shrink a substantial amount; and then (4) stabilizing the fabric by treating the same in the shrunken state with a thermoplastic or thermosetting resin or a cross-linking or reactive agent.

The twist-on-twist or unbalanced plied yarn used herein may be prepared by plying together single ends of the cellulosic yarn with Z twist therein using a Z ply twist. Alternatively, the single ends may have an S twist in which case the ply twist is also in the S direction. The amount of twist in the single ends, whether Z or S, may be varied but usually will fall in the range of ten to thirty turns per inch. The ply twist also may vary over a wide range although about ten to thirty turns, preferably eighteen to twenty turns, are usually employed. The

3,355,785 Patented Dec. 5, 1967 resulting plied yarn may be used as the filling yarn in the case of woven fabric with conventional type yarn of the same or different composition as the warp. Alternatively, the unbalanced plied yarn herein may be used as the Warp only, or in both the warp and fill, depending on the direction or directions in which stretch is desired.

It is to be noted that the fabric shrinkage operation (3) referred to above is not the same as, or equivalent to, slack mercerizing, i.e. the well-known treatment of a fabric with caustic under essentially tension-free conditions whereby the fabric is free to shrink. As a matter of fact, it has been found that slack mercerizing fabric made with the twist-on-twist plied yarn of the type used herein prior to the stabilizing or finishing step, can seriously limit the amount of fabric stretch that is realized. Thus, for example, the maximum stretch obtainable by slack mercerizing one type of woven fabric tWist-on-twist yarn as the filling, followed by stabilizing or finishing, may be as much as 8.0% less than the stretch obtained with the same fabric using the shrinking step of the present process in combination with the other indicated operations. In the present case, the shrinkage operation is carried out with water (preferably at a temperature of from to 210 F.) rather than with a caustic soda mercerizing solution. The success of the invention appears to be dependent, to a very significant extent, on the discovery that twist-on-twist type cellulosic yarns have an extremely high shrinkage potential and that a water wash as contemplated herein takes fullest advantage of this potential.

Without being limited to any particular theory or explanation, it appears that the following technical considerations may account for the unique results obtainable WllIh the present invention:

(1) Stretch is dependent on the amount of crimp in the yarn and fabric shrinkage increases the yarn crimp and, therefore, stretch. As indicated above, the twist-ontwist yarns used herein contains an extremely high shrinkage potential and when these yarns are washed according to the invention, they shrink to form numerous kinks and knots. Thus, when the yarns are put in a fabric using the tensions normally employed in yarn processing (e.g. spinning, twisting, quilling, warping, winding and weaving) and the resulting fabrics are washed in warm water, the fabric shrinks substantially to give a very sig nificant increase in yarn crimp within the fabric. It appears that essentially all of the shrinkage under these conditions is translated into yarn crimping and therefore stretch. Stabilization of the fabric so that the crimp becomes permanent then results in a fabric with practically a maximum stretch potential.

(2) When a fabric is shrunk by slack mercerization, the amount of workable or useable stretch, even in the case where twist-on-twist plied yarns are used, is not equal to the maximum potential or theoretical stretch based on shrinkage. Apparently, this is due to the fact that, in addition to developing crimp, the shrinkage is translated into fiber swelling (or increasing yarn diameter) and fabric stabilization. Both stabilization and fiber swelling take away from the potential stretch that could be theoretically developed if all of the shrinkage which occurs during mercerization could be translated into crimp. In the present process, however, the fabric shrinkage is translated almost completely into crimp as noted above so that the resulting fabric stretch represents essentially the maximum theoretically possible on the basis of fabric shrinkage. I

The unique nature of the present invention is further pointed up by the fact that the twist-on-twist yarns used herein do not themselves possess stretch to any significant extent. Weaving or other processing of the yarn into fabric can thus be carried out under normal conditions. The

made with the elasticity or stretch is developed only when the yarn, whether in skein form or in the fabric, is washed in warm to hot water.

In one of its preferred embodiments, the present invention contemplates the preparation of a woven stretch cellulosic fabric using, in at least the filling, yarns that have been made by plying together two or more ends of cotton yarn or the equivalent, the .ply twist being in the same direction as the twist of the pre-plied ends, i.e. Z singles plied with a Z twist or S singles plied with an S twist. The resulting woven fabric may then be washed in an open width washer, a rope washer or the equivalent where the fabric is in a condition such that it can shrink freely or to desired width at the washing temperature (preferably 140 to 210 F.). The washing operation may be carried out in ten to sixty minutes although it will be appreciated that the time may be longer or shorter provided the desired degree of shrinkage is attained.

The amount of shrinkage which occurs in the washing treatment will vary depending, for example, on the yarn and fabric constructions and the desired degree of stretch. Usually, however, the shrinkage will be in the range of fifteen to thirty percent in the direction or directions where stretch is desired. As a typical illustration of the type of shrinkage visualized herein, it can be stated that forty-nine inch loom state fabrics have been allowed to shrink during washing in the filling direction anywhere from thiry-six to forty inches depending on the fabric weight, construction and weave.

Washing of the fabric also serves to remove any sizing material which may have been added to the yarn in slashing or other processing operations. It has been found advantageous to use a highly water-soluble sizing solution such as carboxymethyl cellulose and polyvinylalcohol to facilitate size removal during the water wash. This size removal also aids the contraction of the fabric.

After washing, the fabric may be either slack dried or tenter dried at minimum width and the desired finishing and stabilizing operations may then be conducted in conventional fashion. Thus, for example, a reactant finish may be applied to the fabric. Such finish may comprise the reactant resin, hand builders, softeners, catalysts. After curing, the fabric is washed, dried and Sanforized. As an alternative to using a reactant finish, the fabric may be treated with conventional thermoplastic or thermosetting resin finishing techniques (e.g. pad, dry, cure, wash, dry, and Sanforize). It will be appreciated that the particular conditions and operations selected for practicing the invention will depend on the fabric involved and the ultimate results desired. For example, in the case of heavy all cotton fabrics, the preferred method to obtain maximum fabric contraction and stretch according to the invention is to rope wash, put the fabric on the tenter frame, and pre-Sanforize followed by finishing in any desired fashion.

In order to develop or enhance the esthetic properties of the finished fabrics, the finished fabrics may be given a post-mercerization followed by a post-curing operation. However, it has been found that the same effects offered by post-mercerization, e.g. improved abrasion properties, can be obtained by appropriate additives to the finishing bath so that post-mercerizing is not essential.

The invention described herein is useful with respect to continuous or spun yarns made up entirely or in part of natural or regenerated cellulosic fibers. Blends of any such fibers with polyesters, acrylics, and/or other synthetic fibers (for example blends containing 50%, or more or less, cellulosic fiber), may also be used herein.

Suitable resins and cross-linking or reactive finishes useful herein include any of those conventionally employed for finishing cellulosic fabric. Thus, for example, the finishes described in copending applications Ser. No. 153,021, filed Dec. 4, 1961, now US. Patent No. 3,265,- 963, and Ser. No. 156,859 filed Nov. 17, 1961, respectively, may be used in the manner described therein, the

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subject matter of said applications being incorporated herein by reference. Typical thermosetting resins for use herein are the triazones, ureaformaldehyde, methylated urea formaldehyde, ethylene urea formaldehyde, and alkyl-substituted ethylene urea formaldehyde resin, melamine formaldehyde, methylated melamine formaldehyde, dicyandiamine formaldehyde, phenol formaldehyde, ketone formaldehyde, thio-ureas and similar modifications with formaldehyde guanidine formaldehyde, resins based on acetaldehyde, benzaldehyde, butyraldehyde, resins using higher aliphatic blocking groups to replace methyl such as ethyl, propyl, butyl, etc., modified glycol acetalformaldehyde, pentaerythritol acetalforrnaldehyde, and mixtures of one or more of the above resins with or without the addition of other resins, such as epoxy resins, natural and synthetic rubbers, based on butadiene, or the like, acrylate homopolymers, copolymers, terpolymers, particularly those containing reactive groups such as acrylic and methacrylic acid.

Examples of crosslinking reactants are epichlorohydrin, formaldehyde, and vinyl sulphones while thermoplastic resin finishes include acrylic and vinyl resins, polyurethane, etc. As noted earlier, the finish selected will depend on the type of characteristics desired over and above stretch, e.g. wash and wear, although obviously the finish as applied should not significantly detract from the stretchability and recovery properties imparted by the preceding treatments.

The process of the invention may be applied to any type of fabric, e.g. plain, twill or basket weaves, etc., provided the construction is sufficiently open to accommodate the degree of shrinkage which is desired without buckling or otherwise distorting the fabric.

The invention is illustrated, but not limited, by the following examples:

Example 1 This example compares the stretch characteristics of (l) fabric processed according to the invention using rope washing and (2) fabric processed in the same way except that the washing step is replaced by slack mercerization. Three types of weaves are used, namely, plain, twill, and basket. The data shown in Table I illustrates that the slack mercerized fabrics all had essentially the same stretch potential regardless of the weave or weight of the fabric. The fabrics which were rope washed and otherwise processed according to the invention showed substantially greater stretch potentials in every instance than the slack mercerized fabrics with a variation in stretch dependent on the individual characteristics of the fabric involved.

TABLE I.-A COMPARISON OF THE AFFECT 0F SLACK ME a COTTON FABRICS MADE WITH TWIST-ON-TWIST 292 FILLING YARNS USING PLAIN, TWILL, AND BAsKE l WEAVES. THE WARP YARN WAS COTTON.

Slack Mercerized Percent; Non- Weave Percent Stretch Reeoverable after two hours 1 2.01 2.19 Basket 16. 25 1. 25

Average 16. 15 1. 81

Rope Washed Percent Non- Weave Percent Stretch Recoverable after two hours 20.0 1. 25 24.4 2.19 Basket 28. 8 3. 10

Average 24.4 2

The above data shows that slack mercerization develops crimp but this crimp is not completely useable as stretch. On the other hand, the fabrics processed according to the invention develop the crimp in a way which can be translated to a greater stretch potential.

Example 2 Three all cotton twill fabrics were woven with twiston-twist filling. The filling was prepared by plying two ends of 30/1 cotton yarn using 21 turns per inch in the Z direction, the preplied ends having 16 turns per inch in the Z direction. The warp was 30/ 1. Loomstate width was 49 inches. An 8% solution of carboxymethylcellulose was used to size the yarns in the slashing operation.

After weaving, the fabric was treated as follows:

( 1) rope washed at 160 F. for thirty minutes;

(2) tenter dried at 250 F. at minimum width (40 inches);

(3) Sanforized to straighten patterns;

(4) finished by applying thereto a composition comprising Triazine resin, 1.0% Z NO catalyst, 2.0% amine hydrochloride catalyst, 2% acrylate polymer, 1% polyvinyl acetate, 4% polyethylene softener, balance water, and curing at 350-375 F. for 1 /22 minutes;

(5) washed in water for twenty minutes;

(6) dried at 250-300 F. on a tenter frame, width 39-41 inches.

The results obtained in testing the above fabrics for stretch and wash-wear characteristics are set forth below:

TABLE II Sample N o 1 2 3 Weave Construction 92 x 51.0 98 x 51. 7 08 x 50. 7 Width 41. 375 41.000 41. 375 Ox/Sq.Yd 5. 73 5. 80 6.00

ds./16 2. 43 2. 42 2. 32 Tensile (grab) 68 x 51 59 x 52 61 x 57 Abrasion (war 836 711 644 Dry wrinkle rec. 130 x 121 135 x 133 122 x 121 0 (hr Appearance 4. O 4. 0 4. 0 Elongation potential, percent... 19. 9 20. 1 19.8 Growth alter 5 min. relaxation,

percent 4. 0 4. 0 4. 0 Growth after 2 hrs. relaxation,

percent 3. 0 3. 0 3. 0

1 Twill.

2 None.

It is to be noted that the elongation or stretch potential for each of the treated fabrics was approximately with relatively low loss in fabric width (49 inches to about 41 inches). The value of 4.0 represents outstanding overall appearance. The dry wrinkle recovery values were also indicative of outstanding wash/wear characteristics. The tensile and abrasion results were also good for this type of product.

While the invention has been specifically described above using the twist-on-twist yarn as the filling yarn to give stretch in the filling direction, it is within the scope of the invention to use this type yarn as the warp yarn only, or as the warp and filling yarns, to obtain stretch in the warp direction or warp and filling directions, respectively. Additionally, while the invention is illustrated with particular reference to cotton yarn, other yarns or fabrics, made from either natural or regenerated cellulose, or combinations thereof with other yarns, natural or synthetic, may be effectively used herein. Furthermore, while the invention is of particular advantage in the case of woven fabric, knitted goods or yarns per se may be processed in the manner described herein. Hence, the scope of the invention is defined in the following claims wherein.

I claim:

1. A process for preparing a cellulosic stretch fabric which comprises 1) providing a plied yarn made by plying together at least two ends of cellulosic yarn having an initial twist therein which is in the same direction as the ply twist, said ply twist being accomplished without significant stretching of the yarn and the degree of twist being less than that which will cause the yarn to snarl or kink; (2) making a fabric with this plied yarn; (3) washing the resulting fabric so that the fabric shrinks; and (4) then stabilizing and finishing the fabric by treating with a material selected from thermoplastic and thermosetting resins and cross-linking or reactive agents.

2.. The process of claim 1 wherein the fabric is slack mercerized after washing.

3. The process of claim 1 wherein the amount of twist in the ends before plying is in the range of 10-30 turns per inch and the amount of ply twist is also in the range of 10-30 turns per inch.

4. The process of claim 3 wherein the washing operation is carried out with water at a temperature of from to 210 F. and the shrinkage amounts to from 1530% in the direction of stretch.

5. The process of claim 4 wherein the fabric is dried at minimum width before said stabilizing and finishing operations.

6. The fabric obtained by the process of claim 1.

7. A process for preparing a cellulosic stretch fabric which comprises 1) providing a plied yarn made by plying together at least two ends of cellulosic yarn having an initial twist therein which is in the same direction as the ply twist, said ply twist being accomplished without significant stretching of the yarn and the degree of twist being less than that which will cause the yarn to snarl or kink; (2) weaving a fabric with this plied yarn; (3)

washing the resulting fabric so that the fabric shrinks and (4) then stabilizing, mercerizing and finishing the fabric by treating with a material selected from thermoplastic and thermosetting resins and cross-linking or reactive agents.

8. A process for preparing a cellulosic stretch fabric which comprises 1) providing a plied yarn made by plying together at least two ends of cellulosic yarn having an initial twist therein which is in the same direction as the ply twist, said ply twist being accomplished without significant stretching of the yarn and the degree of twist being less than that which will cause the yarn to snarl or kink; (2) weaving a fabric with this plied yarn as the filling yarn; (3) washing the resulting fabric so that the fabric shrinks and (4) then stabilizing and finishing the fabric by treating with a material selected from thermoplastic and thermosetting resins and cross-linking or reactive agents.

9. A process for preparing a 'cellulosic stretch fabric which comprises (1) providing a plied yarn made by plying together at least two ends of cotton yarn having an initial twist therein which is in the same direction as the ply twist, said ply twist being accomplished without significant stretching of the yarn and the degree of twist being less than that which will cause the yarn to snarl or kink; (2) weaving a fabric with this plied yarn as the filling yarn; (3) washing the resulting fabric with warm to hot water so that the fabric shrinks a substantial amount; and (4) then stabilizing and finishing the fabric by treating with a material selected from thermoplastic and thermosetting resins and cross-linking or reactive agents.

10. A process which comprises preparing a plied yarn by plying together at least two ends of cellulosic yarn which have an initial twist therein in the same direction as the ply twist, said ply twist being accomplished without significant stretching of the yarn and the degree of twist being less than that which will cause the yarn to snarl or kink; and washing the resulting twist-on-twist plied yarn in warm to hot water and in the relaxed condition whereby said plied yarn shrinks substantially.

11. The yarn obtained by the process of claim 10.

References Cited UNITED STATES PATENTS 8/1851 Mercer 8-125 8 Dworsky et a1. 57164 X Lawton 5'7--164 X Foster 28-76 Seltzer 28-76 MERVIN STEIN, Primary Examiner.

L. RIMRODT, Assistant Examiner. 

1. A PROCESS FOR PREPARING A CELLULOSIC STRETCH FABRIC WHICH COMPRISES (1) PROVIDING A PLIED YARN MADE BY PLYING TOGETHER AT LEAST TWO ENDS OF CELLULOSIC YARN HAVING AN INITIAL TWIST THEREIN WHICH IS IN THE SAME DIRECTION AS THE PLY TWIST, SAID PLY TWIST BEING ACCOMPLISHED WITHOUT SIGNIFICANT STRETCHING OF THE YARN AND THE DEGREE OF TWIST BEING LESS THAN THAT WHICH WILL CAUSE THE YARN TO SNARL OR KINK; (2) MAKING A FABRIC WITH THIS PLIED YARN; (3) WASHING THE RESULTING FABRIC SO THAT THE FABRIC SHRINKS; AND (4) THEN STABILIZING AND FINISHING THE FABRIC BY TREATING WITH A MATERIAL SELECTED FROM THERMOPLASTIC AND THERMOSETTING RESINS AND CROSS-LINKING OR REACTIVE AGENTS. 